1. Field of the Invention
The present invention relates to improvements in or to blood oxygenators
2. Description of the Prior Art
The artificial lung or blood oxygenator is usually used for intracardiac surgery. Its primary role is to substitute for respiratory function, that is, blood gas exchange.
With aid of a pump, this apparatus maintains the blood circulation throughout the whole human system, regardless of cardiac conditions, such as arrest, cardiotomy and so forth.
Such an artificial circulatory operation is called extracorporeal circulation. In the conventional method with the above-mentioned devices, a large amount of the blood was required to prime the whole apparatus, and many blood donors were necessary to conduct intracardiac surgery. This frequently caused the homologous blood syndrome (a kind of antigen-antibody reaction intensified by such as artificial perfusion), and postoperative serum hepatitis.
In recent years, there has been provided a reduction in the priming blood volume so that the bubble oxygenator is re-recognized for its practical value. Many attempts have been made to compact the apparatus. At the present time, however, there have yet been unsettled problems in the priming volume, trauma to the blood components, etc.
Further, some of commercialized oxygenators have an oxygenating tube of partitioned structure to prevent collection of bubbles in the upper portion, when the tube tipped, and moreover some of them have baffle boards to promote oxygenation of blood by stirring. However, such structures cause disadvantages as mentioned below. The partitioned structure is prone to further agglomeration of the oxygen bubbles and separation of the bubbles from blood, while insertion of baffle boards in the tube is liable to cause excessive stirring of the blood resulting in hemolysis thereof. Still further, the oxygen demand by each individual is different according to the patient, that is, to their parameters such as the body weight, body temperature, etc. Supersaturation of blood promotes denaturation of the plasma or destruction of blood cells which causes embolism of various types. On the contrary, insufficient oxygenation of the blood brings the patient into a hypoxic state which often gives ill-effects upon his convalescence.
The oxygenator according to the prior skill had the disadvantage that oxygenators of various sizes had to be prepared so as to comply with the blood demands or body weights of each patient (the circulating blood volume is approximately 1/13 of the body weight). Another disadvantage is that if the mesh which surrounds debubbling material is too small, microparticles of larger size may be caught in the mesh to clog, and inversely if the mesh is too large, micro particles such as of smaller size, may pass through the mesh. To prevent such phenomena, a special filter was required in the blood circuit of the conventional oxygenator. However, most of the microfilters commercialized are prone to be clogged, which increases the resistance of the blood flow, with destruction of the blood cells. In addition there have been some problems in the heat-exchanger for thermo-conduction.
A first object of the present invention is to provide an oxygenator of compact structure which secures a low-priming volume perfusion.
A second object of the invention is to provide an oxygenator which maintains adequate oxygenation with least blood trauma.
A third object of the invention is to provide an oxygenator which is equipped with a capacity-control-device of the oxygenating tube to meet the oxygen requirement varied with patient parameters.
A fourth object of the invention is to provide an oxygenator which is equipped with (duplicate) microfilter of gravity drainage that consists of one relatively coarse mesh enveloping (over) the debubbling chamber and of one or more than one fine mesh covering over a lower portion of the coarse mesh; no conventional filter is required in the blood circuit thereof.
A fifth object of the invention is to provide an oxygenator which is equipped with the blood reservoir that incorporates a heat exchanger.
Other and further objects of this invention will become obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.